Recent studies have discussed changes within the politics of the urban poor in Latin America. One perspective finds such politics limited to local material needs petitioning by isolated groups. By contrast, I found a community organization in urban Mexico that was sponsored by another group, and brought into national political efforts and debates by that sponsor. Sponsorship, as a form of relationship between allies, is linked to the grievances felt by Mexican citizens, and these grievances are analyzed as affecting the political opportunity structure of the Mexican urban popular movement. The sponsor brought substantial benefits to the community organization, but the latter organization also suffered from the relationship. The examination of sponsorship between the urban poor and the middle-class allies reveals both benefits and pitfalls.